Mysterious Corrosion pattern on aluminum hull

[BC Coast Pilot]

Same for the zincs on my outboard? Should I be changing them over?

Yes, although most manufacturers supply aluminum anodes for outboards there are some jobber suppliers. Also you shouldn't mix and match. Switch the entire system to Aluminum Anode.(tabs, thruster etc)

 

[pcaker]

I have a 16’ Lifetimer. I got it done at Tri-City blasting in Poco, and since I was on a budget at the time, I told them to go as far as $200 would get it. They definitely went above and beyond, but I still had to remove some of the epoxy primer myself. I pulled the boat off the trailer in my driveway, and sanded the rest off with a 120 grit sanding pad on an angle grinder, being careful not to eat into the metal. I then finished by sanding with an orbital sander to buff out any scratches. I would expect to pay a lot more than I did before n 2016 to have the whole boat done.

Thanks for info

 

[Bill 310]

We use zinc anodes on our welded aluminum boat.

We went to a 50% larger set of zincs this year, Last years smaller set was 2/3rds gone

New Barrier and Bottom paint in the spring

Moored year round at Reed Point

When to Use Zinc Anodes or Aluminum Anodes on Your Boat

Zinc and Aluminum anodes each have their pros and cons. Find out when it's best to use a zinc or aluminum anode, and they're benefits and downsides, here!

citimarinestore.com

 

[BC Coast Pilot]

We use zinc anodes on our welded aluminum boat.

We went to a 50% larger set of zincs this year, Last years smaller set was 2/3rds gone

New Barrier and Bottom paint in the spring

Moored year round at Reed Point

When to Use Zinc Anodes or Aluminum Anodes on Your Boat

Zinc and Aluminum anodes each have their pros and cons. Find out when it's best to use a zinc or aluminum anode, and they're benefits and downsides, here!

citimarinestore.com

I would consider Reed Point brackish no?

 

[Bill 310]

I would consider Reed Point brackish no?

I was thinking that as I read that report.

I think I will go talk to the folks at the SFU research centre and ask the folks at the Marina who did our bottom refresh.

Of course now I will go find out and report back

I found this paper

On the physical oceanography of Burrard Inlet and Indian Arm, British Columbia

Learning, knowledge, research, insight: welcome to the world of UBC Library, the second-largest academic research library in Canada.

open.library.ubc.ca

Now I need to track down the author

This Forum is an amzing source of knowledge and polite questioning

 

[BC Coast Pilot]

We use zinc anodes on our welded aluminum boat.

We went to a 50% larger set of zincs this year, Last years smaller set was 2/3rds gone

New Barrier and Bottom paint in the spring

Moored year round at Reed Point

When to Use Zinc Anodes or Aluminum Anodes on Your Boat

Zinc and Aluminum anodes each have their pros and cons. Find out when it's best to use a zinc or aluminum anode, and they're benefits and downsides, here!

citimarinestore.com

Whats the salinity at Reed Pt.?

Galvanic Series, or Nobility Chart for Dissimilar Metals

Use this chart to avoid galvanic corrosion in seawater when different metals come in to contact. Alloys with higher nobility are at the top, and metals that are less noble (or more base) are at the bottom. How to read and apply the Galvanic Series chart above Galvanic corrosion of the least...

fairwindfasteners.com

 

[Bill 310]

Whats the salinity at Reed Pt.?

Galvanic Series, or Nobility Chart for Dissimilar Metals

Use this chart to avoid galvanic corrosion in seawater when different metals come in to contact. Alloys with higher nobility are at the top, and metals that are less noble (or more base) are at the bottom. How to read and apply the Galvanic Series chart above Galvanic corrosion of the least...

fairwindfasteners.com

At this point in time I don't know what the salinity level is . Once I know I will share it here,

I can tell you that even without using my Secchi Disc that the water has low turbidity at our slip.

​

 

[BC Coast Pilot]

At this point in time I don't know what the salinity level is . Once I know I will share it here,

I can tell you that even without using my Secchi Disc that the water has low turbidity at our slip.

​

We typically load ships at Pacific Coast Terminals using a brackish factor of 1.018 . Seawater is 1.025, Freshwater being 1.0
Above 3rd narrows is probably even fresher in winter, maybe 1.012

 

[pcaker]

I have a 16’ Lifetimer. I got it done at Tri-City blasting in Poco, and since I was on a budget at the time, I told them to go as far as $200 would get it. They definitely went above and beyond, but I still had to remove some of the epoxy primer myself. I pulled the boat off the trailer in my driveway, and sanded the rest off with a 120 grit sanding pad on an angle grinder, being careful not to eat into the metal. I then finished by sanding with an orbital sander to buff out any scratches. I would expect to pay a lot more than I did before n 2016 to have the whole boat done.

Thanks for info, I am increasingly inclined to get bottom paint blasted off. I know that glass beads will not harm the aluminum surface, but I suspect that commercial outfits will want to use a more aggressive abrasive for speed and economy. Anyone know a good compromise abrasive?

 

[InterMechanico]

Beep Bop Bope

I would try this before blasting. No rough surface when you’re done. It does work very well and is water soluble, but PPE is required.
Coveralls, Eye Protection, Respirator and thick nitrile gloves.

High pressure Steam cleaning after application is apparently quite effective as well.

 

[pcaker]

Hi InterMechanico, what is "this" you suggest I try?

 

[InterMechanico]

Hi InterMechanico, what is "this" you suggest I try?

Sorry!

Aircraft Paint Stripper - Pro Form

proformproducts.com

 

[pcaker]

Sorry!

Aircraft Paint Stripper - Pro Form

proformproducts.com

Thanks

 

[Rayvon]

For those of us that have fiberglass boats,NEVER use paint stripper to remove bottom paint,it will also remove your gelcoat if left long enough.

 

[Max123]

I'm curious - I have an aluminum boat that came with bottom paint (Epoxy + Trilux II). The vast majority of my usage is fresh water, and the boat is stored out of water on a trailer - the bottom paint really does nothing for me, and a bare hull would have been preferred.

No evident corrosion problems, peeling paint - nothing. Is there any reason at this point to have it blasted off or just leave it alone? Is there any risk of anything going on behind the paint that I wouldn't know about?

 

[Brando]

leave it alone for now. you have options in the future when the trilux is done but not worth messing with until that time.

When the paint gets corrosion behind it you’ll know. Properly applied epoxy lasts for quite awhile if they did the acid wash and conversion coating you should have many years trouble free